It does implement stochastic synth but using grains (or sound particles).
The one I’m looking for is a procedure invented by Xenakis as well which he called Dynamic Stochastic Synthesis, consisting on the gradual modifications in a waveform’s amplitude by means of stochastic algorithms, all this at the sample level.

Xenakis’s DSS implementation constructs the waveform with stochastic
functions on the lowest level, and tries to limit this space with x/y
barriers. This gives a wild and unique sonic space creating an interesting
metaphor between waveform and higher order sonic forms. But don’t imagine
to obtain all kind of complex sounds.

Stochos needs at least some waveform on the grain level to construct
higher level structures. Complex destruction/construction of the waveform
can be obtained with Cosmos versions, since it has a controlled feedback
mechanism, but this version is still not available, since I wish to manage
to run them on Max5 first!

There have been attempts to make objects that deliver stochastic synthesis true to Xenakis’ ideas. They didn’t work very well however and did not offer the kind of control expected. Doing this within the context of a max external proved to be challenging, apparently, although I don’t know much about the details. The difficulty was the varying cycle duration, if I remember correctly.

It is fairly easy however to make a non-realtime version in max. Just stick to the rules and that’s it. What the rules are can be understood best overhere: http://www.sergioluque.com/thesis.html, a former sonology student who researched Xenakis’ model and works, and removed some of the haze surrounding this matter. He also suggested an addition to the model, which is stochastic concatenation of dynamic stochastic synthesis. Two pieces are presented as well, to me among the best ever made using this model.

good to have news from the developer!
I’ll be glad to test your next cosmos version, I think it
goes more into what I had in mind,

By the way I have tested an interesting form of iterated synthesis (at the low level)that you might like to try: CFFM (cross feed-back FM), the patch is very simple, only 2 cycle in mutual frecuency feedback. You can find the patch in an article by Miranda_VAsalamakis: